. >> reporter: but the horror stories that came from his virginia estate, the deprivation, the beatings, hangings, electrocutions and drownings of dogs that refused to fight were all true. >> come on, bud. good boy! >> reporter: that's what makes leo so remarkable. as a former vick fighting dog, he was once described as a ticking time bomb. but today? what words would you use to describe leo? >> clown... lover boy, kiss me... >> reporter: she is a certified trainer whose los gatos dog rescue group took leo in and focused on his gentle nature. >> our pack rescued him in december 2007. and within five weeks, he was registered as a therapy dog. >> come on, sweetheart. >> reporter: that's right. this broad shouldered pit bull now wears a clown's collar to a mountain view cancer care center once a week to love and be loved by patients who know what it's like to be hurting. >> when i see him, it's joy. i mean, you know, he just makes me feel good inside. you know? so good to feel good these days. >> reporter: ruth adams has been seeing leo for two years and they seem to have formed a close bo